Adobe reader 8.1 onwards - pdfs that can generate barcodes

Could someone explain to me how these barcodes work?
And whether it implies what I think it does?

This is years-old technology now but...well, I never personally encountered a pdf with special programming before.

Was recently filling in an application form available in a special pdf format. Instructions said that when you're done, you press the 'validate' button on the form, and a barcode will be generated.

I was doubtful that that button could work in Adobe Reader but it did, and barcodes got generated. I printed them out along with the finished form.
Googling didn't get me anywhere near to understanding what these barcodes were for, although one user article suggested that:

The barcodes contain the data you put into all 5 pages of your application so that actually you don't need to send the rest of the application, just the barcodes. Also that scanning up these barcodes at the other end is enough to regenerate the form with your answers in it.

I was tempted to just send the barcode sheet in the post. I'm fascinated ... but unsure if I understood correctly.


My question:
Can a barcode really carry that much data? I thought they were only for generating unique number codes/IDs.

Does this mean that there is actually another option for portable data drives besides USB sticks : barcodes. ???